4 REASONS FOR THE STUDY OF BIOLOGY 



Animals also carry disease germs ; flies, mosquitoes, rats, and cats 

 are well known as spreaders of diseases. 



From a monetary standpoint, insects do much harm. It is esti- 

 mated that in this country alone in 1924 they were responsible for 

 considerably over $2,000,000,000 worth of damage by eating crops, 

 stored food, and other things. 



The Uses of Animals to Man. — We all know the uses man 

 has made of the domesticated animals for food and as beasts of 



Cows in a model stable, with milking machines in operation. There are 

 many state laws and city ordinances for the regulation of dairies and the sale 

 and distribution of milk. 



burden. But many other uses are found for animal products, 

 and materials made from animals. Wool, furs, leather, hides, 

 feathers, and silk are examples. The arts make use of ivory, tor- 

 toise shell, corals, and mother-of-pearl ; from animals come per- 

 fumes and oils, glue, and various other commodities. 



Relations of Plants and Animals. — Most plants and animals 

 stand in a relation of mutual helpfulness, plants providing food 

 and shelter for animals, and animals giving off waste materials 

 useful to plants in the making of food. We also learn that plants 

 and animals need the same conditions in their surroundings in 

 order to live : water, air, food, a favorable temperature, and usually 



